Conventionally, a pusher dog of a storage conveyor, as described in Japanese Patent Publication No. Sho 57-59166, includes a hook portion which is detachably hooked on a truck and an external force action surface which are concentrically formed above a pivotal shaft. According to such a pusher dog, the length of the upper portion of the pusher dog and the turning radius thereof are elongated with respect to the pivotal shaft of the hook portion, with the result that a large amount of space, in a vertical direction between the track of the driving conveyor chain and the running track of the truck which is engaged with the pusher dog, is necessary. However, this raises the problem that the occupied space of the conveyor is increased.
In order to solve the foregoing problem, inherent in the conventional pusher dog, a new and improved pusher dog has been developed. This new and improved pusher dog is disclosed in Japanese Patent Application No. Hei 6-99130. As shown in FIG. 2 and according to the aforementioned Japanese Patent application, the pusher dog D includes only a pusher surface P, formed above the pivotal shaft A, for pushing a pusher dog engaging member B which is vertically elongated downward from the lower surface of the front wheel of the truck, and an external force action surface formed at the lower end portion T of the pusher dog D under the pivotal shaft A.
However, such a pusher dog D, wherein an external force action surface is formed at the lower end portion T thereof, has another problem in that it is difficult to tilt the pusher dog D if using the conventional tilt operation member mounted on the lower surface of the frame of the truck.